I understand the pressure to put your child in their own bed. You want to get back to having your own bed, etc. The child does not understand at this age very well - they can easily take it as a rejection leading to more clingy behavior, delayed bed times, the vomiting, etc. You have to help the child see this transition as a privaledge, a good thing that they WANT, and not as a rejection, punishment, or scary place to be.
If the child has already taken this transition/new space in a negative light you may need to wait 3-6 months before you try again while the child becomes more secure and gets over the anxiety that is now there. You need to deal with the damage that has already been done before you try again.
Try to get your spouce to help with this as well by not being irritated or intolerant - remind him he will get his attention soon enough but the tension will only delay that for everyone. Guys seem to be the big problem behind pushing for earlier breastfeeding/sleep weaning while more often the women I talk to find these times to be pleasant and they are not eager to give them up. Y'all have a lifetime together, you only get a few years of your child needing you so much - he can be the bigger man and help you keep your cool as the transition is being made.
I co-slept with my child for the first several years (sometimes my husband who did not agree with co-sleeping would go to the couch or the spare bed) and gradually weaned her to her own bed. She was in her own room by the time school started & she has never been afraid of anything. Use the same tactics for weaning your child to their own room as one would use for weaning from breastfeeding:
*Take the time to let them help you pick out the space and make it their own. When they have made the space comfortable to them and it is "theirs" (even if it looks really tacky to us) they will be more willing to stay in it.
*Plan an extra few minutes (I averaged 30) to ease the sleep transition with you there... read, cuddle, assure them they are special to you no matter what & that you WILL be there if ever they need you.
*Don't try to change too many things in their life at one time. If you are going to adjust sleep - leave off diet, study, activity changes till this is done. Kids don't adjust as easily as we want them to because they have a small experience reference to make cognative connections with.
*Set clear rules/expectations but keep it simple. Show them an analog clock then mark what is bed time, wake time, etc and tell them "from [time] till [time] I am going to be asleep... and I expect you to be asleep too. I do not want you to come into my room from this time to this time because I will be asleep; if you wake up between these times I expect you to play quietly in your room."
*While the child is co-sleeping before you reattempt the transition: When the child is in bed with you make a solid rule that they will only sleep in a certain space and if they roll around/kick/etc too much you will tell them to leave because YOU have to have your sleep too. This can actually be part of hte transition. My child had to be sent out of my room a few times for this reason because it was more of a "are you really going to bed or can I push it?" test.
*After the child is put to bed, go to bed with your spouce. You need time together, the child needs to believe you have gone to sleep and s/he is not missing anything. This is a great time to get a relaxing bath, massage, or share a glass of wime/beer - whatever.
*Avoid exposing your child to ideas that would make them fear being alone in their room. You'd be surprised how many very small children are exposed to horror flicks and then the parents are frustrated the kid is afraid of the dark, closets, sounds, etc. Kids pick up everything they are exposed to... but they do not have the ability to differentiate fact from fiction and with the limited experience they do not process it as we would anticipate. Keep those horror flicks, suspenceful TV shows, and conversations about tense subjects out of ear/eye shot of your child till they are older (10+).
I hope my experiences (and hard learned lessons) help you find the peace you need, to be the wonderful parent you are. Do what feels best for your family now and they will be easier to deal with as they grow. Good luck!